Thanks for the comments. Looking back I see that I did not have my Minus Violet filter in. The image train was as follow's. AR5 telescope - focal reducer - IR filter - DSI II color camera. Used Envisage to capture. Saved as BMP. Processed with Nebulosity which I just purchased that same night. Had no idea what I was doing. Still need to read manual. There is an action in Nebulosity to tighten stars which does seem to help. The only halos I seem to get are from very bright stars but I do not find them to be a problem.